1. Field of the Invention
The present invention relates to a toner, a method of manufacturing the toner, a developer, a two-component developer, a developing device, and an image forming apparatus having the developing device.
2. Description of the Related Art
A toner is used to visualize a latent image in various image forming processes, and one known example thereof is an electrophotographic image forming process.
An image forming apparatus for forming images by using an electrophotographic system includes a photoreceptor, a charging section, an exposure section, a developing section, a transfer section, a fixing section and a cleaning section. The charging section charges the surface of the photoreceptor in a charging step. The exposure section irradiates a signal light to the surface of the photoreceptor in a charged state to form static latent images corresponding to image information. The developing section supplies a toner in a developer to the static latent images formed on the surface of the photoreceptor to develop static latent images thereby forming toner images in the development step. The transfer section transfers toner images formed on the surface of the photoreceptor to a recording medium in a transfer step. The fixing section fixes the transferred toner images to the recording medium in the fixing step. The cleaning section cleans the surface of the photoreceptor after transfer of the toner images in a cleaning step. The image forming apparatus develops static latent images to form images by using a one-component developer containing only a toner or a two-component developer containing a toner and a carrier as a developer. The toner used herein is resin particles formed by dispersing colorant, a release agent, etc. in a binder resin and granulating them.
Since the images forming apparatus using electrophotography can form images of good image quality at a high speed and inexpensively, they are utilized, for example, an copying machines, printers, and facsimile units and popularization of the image forming apparatus using electrophotography is remarkable in recent years. Correspondingly, a demand for the image forming apparatus has become severer. Among all, an importance is attached particularly to higher fineness and higher resolution of images formed by the image forming apparatus, stabilization of image quality, increase in the image forming speed, etc. For attaining them, investigation is indispensable both on the image forming process and the developer.
With respect to the higher fineness and higher resolution of the images, with a view point that reproduction of static latent images at high fidelity is important on the side of the developer, decrease in the size of toner particles is one of subjects to be solved, for which various proposals have been made.
However, in a case of manufacturing a toner with a small particle size of 4 to 6 μm in an average particle size while intending to obtain higher image quality, since toner particles having a particle size of 2 μm or less contained in a toner with an average particle size of 4 to 6 μm occupy the carrier surface even when the content in the entire toner particles is low to lowers the chargeability of the carrier, a supplied toner cannot be charged sufficiently to cause toner scattering upon continuous image output. Further, toner particles having a particle size of 2 μm or less results in various undesired effects in the improvement of the image quality, such as spent of the toner to the carrier surface, and filming of the toner to the photoreceptor and a developing sleeve.
For solving such problems, Japanese Patent Unexamined Publication JP-A 2005-196142 discloses a toner in which the ratio of particles having a circle-equivalent diameter of 0.6 to 2.0 μm as measured by a flow particle image analyzer is 0 to 5% by number, a weight average size is 4 to 7 μm, the ratio of particles of from 3.17 to 4.00 μm is 10 to 40% by number, the ratio of particles of 4.00 to 5.04 μm is from 20 to 40% by number, the ratio of coarse particles of 12.7 μm or more is 0 to 1.0% by weight, and the ratio (D4/D1) of the weight average size (D4) and the number average size (D1) is 1.04 to 1.30 measured by a Coulter counter method. In the toner disclosed in JP-A 2005-196142, the ratio of toner particles with a particle size of 2 μm or less that gives undesired effects in the improvement of the image quality is decreased to such an extent as not giving undesired effects in the improvement of the image quality. Such a toner can be manufactured by previous pulverization using a mechanical pulverizing system and subsequent pulverization by a counter air flow pulverizer.
However, in the toner disclosed In JP-A 2005-196142, it is not consider for the ratio of toner particles having a size larger than the range described above, that is, having a value of 2.0 μm or more as measured by the flow particle analyzer and a value based on the number of less than 3.17 μm as measured by the Coulter counter method. Since the toner of a small particle size with an average particle size of 4 to 6 μm intended for the higher image quality contains toner particles having a particle size in a range not considered in JP-A 2005-196142 and the toner particles in the range also concern generation of the toner scattering, it is difficult to sufficiently prevent fogging caused by toner scattering.
Further, in JP-A 2005-196142, while the ratio of the particles having a circle-equivalent diameter of 0.6 to 2.0 μm attributable to the toner scattering is defined as 0 to 5% by number, since the toner disclosed in JP-A 2005-196142 is a toner manufactured by a pulverization method and the shape of the toner particle is distorted, when a developer containing the toner disclosed in JP-A 2005-196142 is rotated idly in a developing apparatus, it may be a possibility that corners of toner particles are rounded off by collision of toner particles against each other to further generate particles having a circle-equivalent diameter of 0.6 to 2.0 μm.